Spring steel

1. A spring steel comprising, as a chemical composition, by mass %:

C: 0.40% to 0.60%;

Si: 0.90% to 3.00%;

Mn: 0.10% to 0.60%;

Cr: 0.10% to 1.00%;

Al: 0.010% or more and less than 0.050%;

Ti: 0.040% to 0.100%;

B: 0.0010% to 0.0060%;

N: 0.0010% to 0.0070%;

V: 0% to 1.00%;

Mo: 0% to 1.00%;

Ni: 0% or more and less than 0.45%;

Cu: 0% to 0.50%;

Nb: 0% to 0.10%;

P: limited to less than 0.020%;

S: limited to less than 0.020%; and

a remainder including Fe and impurities,

wherein Expressions 1 and 2 are satisfied, and

an appearance frequency of MnS is less than 20%, wherein said appearance frequency is defined as a number of MnS inclusions observed at a ¼ position of a diameter from a surface divided by a number of total inclusions having an equivalent circle diameter of 1 μm or more observed at said ¼ position of a diameter from a surface, expressed as a percentage,

([Ti mass %]−3.43×[N mass %])/[S mass %]>4.0  Expression 1

[Ni mass %]+[Cu mass %]<0.75  Expression 2

here, [Ni mass %], [Cu mass %], [Ti mass %], [N mass %], and [S mass %] in Expressions 1 and 2 respectively represent a Ni content, a Cu content, a Ti content, a N content, and a S content in unit mass%, and

when the spring steel is heated at temperature of 900° C. to 1,050° C. and quenched, and then is tempered such that the tensile strength is 1900 MPa to 2000 MPa, the impact value is 70.0 J/cm 2 or more.

2. The spring steel according to claim 1 comprising, as the chemical composition, by mass%, one or more selected from the group consisting of:

V: 0.05% to 1.00%;

Mo: 0.10% to 1.00%;

Ni: 0.05% or more and less than 0.45%;

Cu: 0.05% to 0.50%; and

Nb: 0.01% to 0.10%.

3. The spring steel according to claim 1 , comprising, as the chemical composition, by mass %, Si: 0.9 to 2.5%.